Bicycles are human powered two-wheeled vehicles having a frame mounted on the wheels, a drive sprocket and chain, pedals and crank for driving the drive sprocket, handlebars, and a seat mounted on a seat post. In recent years there has been a substantial upsurge in the vigorous recreational use of bicycles, and a new type of bicycle frequently termed a mountain bike has been developed for use in climbing and descending rough and steep terrain. In addition to sturdier construction, mountain bicycles often have complicated gearing affording numerous drive ratios, and improved brakes, wheels and wheel suspensions.
Rear wheel suspensions have been improved by the addition of such suspension components as shock-absorber controlled swing arms in place of the rigid bars which are typically found on bicycles.